An interference pattern is observed by Young's double slit experiment.If now the separation between coherent source is halved and the distance of screen from coheren sources is doubled, then now fringe width

Options

A. becomes double
B. becomes ne-fourth
C. remains same
D. becomes four times

Answer

D

Explanation

Frime width `(W) =q(Dlambda)/(d)`
Now, distance between the coherent souces is halved i.e `d'=d//2` and distance of coherent source and screen is doubled i.e `D'=2D`
`therefore " "W'=(D'lambda)/(d)=(2Dlambda)/(d//2)=(4Dlambda)/(d)rArr(W')/(w)=4`
`rArr W'=4W`(becomes four times)